1. Field of the Invention
The present invention relates to a paste-like dentifrice composition. More specifically, the present invention relates to such a composition containing, as its foaming agent, N-long-chain acylglutamate which assures an increased level of safety, in such a manner that the use of this substance does not involve problems such as a change in taste of foods after tooth-brushing.
2. Discussion of the Background
A dentifrice contains as one of its components a foaming agent which provides such actions as a cleaning action, a dispersing and emulsifying action, and a foaming action. A surface active agent is used for this purpose.
A surface active agent used as a foaming agent in a dentifrice composition reduces the surface tension of the composition when used, thereby promoting the cleaning effect of the dentifrice composition, and promotes the dispersion and permeation of various medically effective agents contained in the composition, thereby enhancing their effects. The surface active agent also forms foam when the dentifrice is used, thereby providing the user with a sense of assurance. A surface active agent thus can be said to be an essential component of a dentifrice composition.
A surface active agent to be used as one of the components of a dentifrice composition, therefore, must be able to exhibit excellent performance in, e.g., reducing the surface tension and foaming. In addition, because a dentifrice composition is used in the mouth, the surface active agent contained therein must have satisfactory properties in terms of taste, odor, etc. Hitherto, anionic surface active agents, such as sodium alkylsulfate, sodium acylsarcosinate, .alpha.-olefin sulfonate, and coconut nomoglyceride sodium sulfate, have been used. In particular, sodium alkylsulfate, which is excellent in terms of its performance and taste, is used most commonly. However, the use of this substance as the surface active agent of a dentifrice composition involves a great drawback: after the use of the dentifrice composition, possibly because of the adhesion of the substance in the mouth, e.g., on the taste buds of the tongue or the mucous membrane of the mouth, the taste of food taken in the mouth after tooth-brushing changes. Another problem is that, sodium alkylsulfate when contained in a dentifrice composition slightly stimulate the mucous membrane of the mouth and deactivates the enzyme which has been incorporated as a medically effective agent.
Recently, the level of safety of such surface active agents has been questioned, and various studies have been conducted to enable a safer surface active agent to be used as the foaming agent in a dentifrice composition. A proposal has been made, for example, to use N-long-chain acylglutamate in a dentifrice composition (Japanese Patent Publication (Kokai) No. SHO 45-24480 (1970)). It is said that N-long-chain acylglutamate, which has no toxicity and only very mildly stimulates the skin or the mucous membrane, while possessing excellent cleaning, foaming, and emulsifying action, and is excellent in resistance to hard water, is a very effective foaming agent for a dentifrice composition because of various advantageous properties such as those mentioned above.
With respect to the influence of N-long-chain acylglutamate on the taste of dentifrice compositions, it is reported that, if a dentifrice composition contains a large amount of N-long-chain acylglutamate having a relatively lower acyl group (e.g., coconut oil fatty acid acyl), the composition has a strongly bitter taste (Japanese Patent Publication (Kokai) No. SHO 58-45402 (1983)). Hitherto, however, nothing about the influence of impurities in N-long-chain acylglutamate has been known.